The invention relates to a method for the precision mounting of a first apparatus part on a second apparatus part, the first apparatus part having irregular edges, and the second apparatus part being provided with first positioning means, and the first apparatus part including one or more components positioned on the apparatus part by means of a position reference system.
The invention further relates to an apparatus including at least a first apparatus part and a second apparatus part which are mutually precision-mounted by means of first positioning means on the second apparatus part and second positioning means on the first apparatus part so that components on the first apparatus part are positioned with a well-defined geometrical relationship relatively to structural features on a second apparatus part.
The invention further relates to an apparatus part including one or more components positioned on the apparatus part by means of a position reference system.
The present invention relates to the assembly of planar devices in particular. In mass production of some planar electronic parts, identical devices are replicated on the same substrate (e.g. integrated circuits or micro-mechanical parts (or combinations thereof) on a wafer or electronic displays on a glass plate, etc.) and separated from each other by some sort of cutting process, e.g. a sawing process using a diamond saw. The cutting is performed in predefined scribe lanes whose width and degree of evenness after the cutting are dependent on the particular devices, process, substrate materials and cutting tools in question. Because of this unevenness, it is, however, a common problem to give accurate information on the distance from the outer boundary of the substrate to particular devices or structures on the substrate interior. Hence, the mounting of such cut-out parts based on the outer, uneven, boundary of the part has an inherent inaccuracy originating from the cutting process. This causes problems, when the alignment of a cut-out part in a mounting process relative to another structure has to be made precisely according to the absolute position of a specific component or structural element on the substrate, e.g. the active area of a liquid crystal display or the optical lens of a micro-mechanical, optical device, etc.
The following account of prior art relates to the mounting of a display unit in a mobile telephone.
Display units, in particular liquid crystal displays (LCD) are today placed in a mobile phone by using a carrier or light guide that is mounted on the printed circuit board (PCB). The LCD is positioned on the carrier/light guide, and the carrier and the PCB are mounted on the frame or housing of the phone. The LCD needs to be very accurately positioned on the light guide, so that the display unit is correctly positioned inside the window of the front cover of the frame. Also, the LCD must be extremely accurately positioned with respect to the PCB in order to ensure a safe and reliable electrical contact between the elastomeric connector on the display unit and the corresponding contact portions on the PCB.
The generally flat LCD substrate is positioned on the carrier by means of its outer edges using a frame-like fixture that is mounted on the light guide. The LCD is held between two spring levers on two opposing side edges of the LCD. Thereby, the LCD is claimed and centered in the fixture. The fixture is then mounted on the light guide which is again mounted in the frame by mounting members that can snap into position on the carrier.
The LCD can further be provided with a strip of dual adhesive tape around the front side, so that the LCD is adhesively joined to the inside of the frame. However, with this method of LCD positioning it is difficult to ensure the required accuracy in the LCD position.
The tolerance chain in this assembly is extensive and may sometimes cause the window printing or the front cover to seal the active area of the LCD. This extensive tolerance chain can also result in a loss of contact with the elastomeric connector between the LCD and the PCB.
Beside the extensive tolerance chain in this LCD assembly, this known assembly consists of many parts which make the assembly complicated and relatively labour intensive in order to achieve the required accuracy in the final result.
On this background, it is an object of the invention to provide for a more precise mounting of a first apparatus part having irregular edges on a second apparatus part, thereby improving quality and reducing waste. It is another object of the invention to obtain an assembly that is less labour intensive and easier (and thus potentially of lower cost) to manufacture.
These objects are achieved by the invention as disclosed in claim 1 by laying out at least one distinctive mark by means of the position reference system on said first apparatus part in a well-defined geometrical relationship to said one or more components, by securing second positioning means on the first apparatus part in a well-defined geometrical relationship to the distinctive mark(s) by means of a positioning system, and by mounting the first apparatus part on the second apparatus part by means of said first and second positioning means.
According to the invention, one or more distinctive marks added to the substrate of a first apparatus part by a so-called position reference system used in the production process of the part are used for the positioning and fixing of the part (according to one or more xe2x80x98decisive componentsxe2x80x99 included on the part) with respect to a second apparatus part, said second apparatus part being provided with first positioning means. The relevant distinctive mark(s) is(are) read from the first apparatus part by a positioning system and the information is used to position the part relative to other structures with which it is to be assembled. Second positioning means, designed to co-operate with the first positioning means on the second apparatus part, are secured on the first apparatus part in accordance with the distinctive mark(s) and thus in a well-known geometrical relationship to the xe2x80x98decisive componentsxe2x80x99 on the part. The two sets of co-operating positioning means may hence be designed and positioned on the first and second apparatus parts, respectively, so that when the co-operating positioning means are joined, a controlled geometrical relationship is obtained between the xe2x80x98decisive componentsxe2x80x99 on the first apparatus part and relevant corresponding features on the second apparatus part. The xe2x80x98decisive componentxe2x80x99 on the first apparatus part may e.g. be the active area of an LCD, and the corresponding feature on the second apparatus part may e.g. be the display window of a light carrier of a mobile telephone.
The invention utilises distinctive marks added to an apparatus part during its processing, these distinctive marks having xe2x80x98microscopicxe2x80x99 tolerances as they are e.g. the results of a semiconductor-like process, to control the positioning of decisive components or other structural elements on the apparatus part relative to corresponding features on another part. Thereby the xe2x80x98macroscopicxe2x80x99 positioning of the apparatus part on the body in question is based on the xe2x80x98microscopicxe2x80x99 tolerances of the production process of the apparatus part.
An advantage of the method is that the apparatus part provided with distinctive marks to be used in the positioning and mounting of the part on another apparatus part may be produced in one production process (e.g. a semiconductor process or the like) and used as a xe2x80x98componentxe2x80x99 in a device assembled with another apparatus part in another production process, possibly at different locations. A further advantage of the method is that it is well-suited for automation and hence of course advantageous from a precision and cost perspective, when dealing with large quantities. Since the guiding means ensure a correct position of the first part relatively to the second part, the actual joining of the parts is uncritical, and therefore the parts may alternatively be joined using a manual or semi-automatic assembly without loss of precision. This may be advantageous e.g. in prototype developments or when dealing with small quantities or if manual assembly is attractive for other reasons.
By, as disclosed in claim 2, further, i.e. in addition to the ones laid out by the position reference system, securing one or more additional components or structural elements on the first apparatus part under control of the positioning system using the distinctive marks, a greater flexibility is achieved in allowing the mass production of identical parts in one location and the possible customisation and use of the part in other locations. This is exactly the relevant scenario in many applications of electronic (and other) components for the construction of semi-finished or finished devices.
In a special embodiment of the invention, as stated in claim 3, the apparatus part is a liquid crystal display module including a liquid crystal display with corresponding electronic circuit(s) and electrical connections. Special advantages of the mounting of the display according to the invention are 1) better use of the active display area and 2) better control of the electrical connections between the display unit and other parts, e.g. a PCB.
The cornerstone of the invention is the use of the xe2x80x98distinctive marksxe2x80x99 laid out by a high-precision positioning system. In preferred embodiments of the invention these distinctive marks may be special alignment marks, electrical connections, as stated in claim 4, or pads for electrical connections, the advantages of each being dependent on the particular process, type of apparatus part, positioning system used for the assembly, required precision, etc. Important is 1) that the distinctive marks used are laid out with high precision, 2) that an exact relationship to the location of the decisive parts of the components to be used in the positioning of the part relative to other structures is or may be established and 3) that the distinctive marks are easy to identify for the positioning system used in the assembly process.
The xe2x80x98positioning systemxe2x80x99 may be the position reference system or another positioning system having means for reading the relevant distinctive marks. In a special embodiment of the invention, as stated in claim 5, the positioning system may e.g. be a vision system used in the assembly process, the first apparatus part being joined with other apparatus parts. A xe2x80x98vision systemxe2x80x99 is a pattern recognition system that enables automatic handling of known structures, e.g. by an assembly robot. The vision system must be able to read the relevant distinctive marks on the apparatus part. This has the economic and logistic advantage that the use of the invention may be integrated in a xe2x80x98normalxe2x80x99 assembly chain. The xe2x80x98position reference systemxe2x80x99 is the positioning system used for the layout of the distinctive marks and of the individual layers or steps that constitute the creation of or placement of the components and structural elements in the production process of the first apparatus part. In another special embodiment of the invention, as stated in claim 6, the positioning system is equal to the position reference system. This has the advantage that the positioning means of the first apparatus part can be applied in the same operation and with the same accuracy as the components or other structural elements in question and as the distinctive marks of the part, thus eliminating a link in the tolerance chain.
In special embodiments of the invention, the first positioning means on the second apparatus part with which the first apparatus part is to be joined via its co-operating positioning means are designed with a view to receiving said co-operating positioning or guiding means to obtain a precise and cost-effective mounting of the apparatus part at the same time. The positioning means on the apparatus part may be fixed to the part by gluing, soldering, fastening by screws or the like, depending on the materials, the mechanical constraints, etc. involved. In a preferred embodiment of the invention, as stated in claim 7, the guiding means of the first apparatus part comprise at least two protruding members which are inserted in the receiving means of the second apparatus part comprising a corresponding number of receiving openings. Hereby, a simple and particularly inexpensive way of precision mounting the apparatus parts is obtained. Alternatively, as stated in claim 8, the guiding means of the first apparatus part may comprise at least two apertures which co-operate with the receiving means of the second apparatus part comprising a corresponding number of protruding members. Other joining techniques (e.g. snap fasteners, fastening by screws, glue, adhesive tape, etc.) or combinations thereof may be used, if conditions so permit.
In a preferred embodiment of the invention, the method may be used for the positioning of a first apparatus part (e.g. a display) relative to a second apparatus part, e.g. a light guide, as stated in claim 9, for distributing light to push buttons or the like in an electronic device, e.g. a mobile phone. This has the advantage of enabling low-cost mass production of a vital apparatus part of use in a range of high-volume communications devices and at the same time solving an existing problem.
In another preferred embodiment of the invention, as stated in claim 10, the method may be used for the positioning of a first apparatus part relative to a printed circuit board. This has the economic and technical advantage of reducing the requirements with respect to the tolerances of the layout of the connections on the PCB as well as any connecting members involved.
In other preferred embodiments of the invention, as stated in claim 11, the method may be used for the positioning of a first apparatus part relative to a part of the housing of the apparatus and in particular, as stated in claim 12, to the front cover of the apparatus. This offers additional design options for the designer of the electronic hardware inside the apparatus and a particular simple way of mounting the apparatus part in relation to the housing.
As stated in claim 13, the present invention further provides an apparatus including at least a first apparatus part and a second apparatus part which are mutually precision-mounted by means of first positioning means on the second apparatus part and second positioning means on the first apparatus part so that components on the first apparatus part are positioned with a well-defined geometrical relationship relatively to structural features on a second apparatus part. By providing the first apparatus part with at least one distinctive mark which has a well-defined geometrical relationship to components on the first apparatus part, and while the second positioning means are positioned with a well-defined geometrical relationship relatively to said distinctive mark(s) and to said components, and the second apparatus part has its first positioning means positioned in a well-defined geometrical relationship relatively to said structural features, it is ensured that the critical parts are precision-mounted in the apparatus, thereby enhancing quality, promoting automation in assembly and potentially reducing costs.
In a special embodiment of the invention, as stated in claim 14, the apparatus is a mobile telephone, the production of which is subject to the constraints of producing large quantities of high-performance devices at a low cost, thereby making the use of the present invention advantageous.
As disclosed in claim 15, the present invention further provides an apparatus part including one or more components positioned on the apparatus part by means of a position reference system. Since the part additionally includes at least one distinctive mark laid out in a well-defined geometrical relationship to said one or more components by means of said position reference system, and while positioning means are secured on the apparatus part in a well-defined geometrical relationship to the distinctive mark(s) by means of a positioning system (e.g. a vision system), it is ensured that such apparatus parts may be precision-mounted on other apparatus parts and in an apparatus, thus enhancing quality, promoting automation in assembly and potentially reducing costs.
In a preferred embodiment of the invention, as stated in claim 16, one or more other components or other structural elements are secured to or laid out on the apparatus part under control of the positioning system. This has the advantage of allowing the mass production of identical parts in one location and the possible customisation and use of the part in other locations which provides a greater flexibility in the completion of the finished device.
In other preferred embodiments of the invention, the distinctive marks may be special alignment marks, electrical connections, as stated in claim 17, including pads, the advantages of each being dependent on the particular process, type of apparatus part, positioning system used for the assembly, required precision, etc.
In a preferred embodiment of the invention, as stated in claim 18, the positioning means of the apparatus part include means for establishing electrical contact to another another apparatus part (e.g. a printed circuit board) in the form of a receiving slot for accommodating an elastomeric block with a plurality of individually isolated conducting members. This has the advantage of facilitating the establishing of reliable electrical contacts between the apparatus part and a printed circuit board. The improved accuracy in the connections of the apparatus part to the PCB may be achieved in addition to the precision mounting of the apparatus part relative to another part by designing corresponding positioning means on the PCB.
In special embodiments of the invention, as stated in claim 19, one of said one or more components on the apparatus part is a liquid crystal display and, as stated in claim 20, one of said one or more additional components is a driver circuit for the display.
In a preferred embodiment of the invention, the apparatus part is a liquid crystal display module, the driver circuit is secured to the apparatus part under control of the positioning system, and the distinctive marks are electrical connections (e.g. pads). This is an embodiment that may be used in a variety of electronic devices, including mobile telephones, pagers, electronic calculators, etc.